The present invention relates to a new and improved roller apron framework or strand guide framework --hereinafter sometimes either conveniently referred to as a roller apron or roller apron framework-- for supporting a partially solidified strand in a continuous casting installation, especially for the casting of slabs, comprising a plurality of rollers, especially guide rollers, mounted within the maximum slab width.
The guide rollers or rolls of continuous casting installations are exposed to high alternating mechanical loads during each revolution of the rollers owing to the ferrostatic pressure acting upon the strand shell or skin. In the case of continuous casting installations for the casting of slabs such high alternating mechanical loads can exceed one hundred tons for each roll. Further loading of the rolls occurs due to the shock-like temperature increase at the roll surface each time the same comes into contact with the hot strand. These mechanical and thermal loads, depending upon the strength of the material from which the rolls or rollers are fabricated, require a predetermined roll diameter.
The actually prevailing roll diameter of the rolls or rollers at a roller apron of a given continuous casting plant or installation governs the permissible minimum spacing between the rollers and equally the size of the unsupported surfaces of the strand between such rollers. The mutual dependency between the permissible roller load, the strand width, the thickness of the strand shell or skin, the roller diameter and the spacing between successive rollers, limits the casting speed during the continuous casting of large casting formats or shapes, since there must be prevented damaging bowing-out or dishing of the strand and metal breakouts. Hence, strands having a width of, for instance, 2.5 to 3 meters can not be rationally cast with the heretofore known continuous casting installations.
There is already known to the art a roller apron framework wherein the shafts mounted a number of times in a support arrangement are disposed in each case between the bearings of short guide roller sections. Consequently, it is possible to maintain relatively small the spacing between successive guide rollers in the direction of travel of the strand. This roller apron is complicated due to the numerous bearings and roller sections. Since the rollers only can be disassembled together with their supporting framework each time it is necessary in a cumbersome and time-consuming manner to disconnect the attachment or fastening devices of the supporting framework. Moreover, the bearings themselves are extremely poorly accessible for maintenance and servicing work. Hence, this state-of-the-art roller apron framework or roller apron does not fulfill the requirements for a simple construction conducive to repair work.